Analog Discovery 2 Record not working on sampling frequencies lower than 1 kHz

[abadialali]

Hi Guys, 

 

I am using the Analog discovery 2 board and I want to generate a custom signal with a sampling of 100 Hz. I have modified the record code provided in the SDK and it is working perfectly , but code isn't working with sampling frequencies (hzAcq) lower than 1 kHz, it simply doesn't go into acquisition and doesn't give anything. 

 

Could you pelase let me know what is the issue.   

Below is the code: 

 

#declare ctype variables

hdwf = c_int()

sts = c_byte()

hzAcq =c_double(1000) #sampling freq

nSamples = 4096

rgdSamples = (c_double*nSamples)()

cAvailable = c_int()

cLost = c_int()

cCorrupted = c_int()

fLost = 0

fCorrupted = 0

 

fs = hzAcq.value

fl = 100

fu = 1000

N = nSamples

t = np.linspace(0,N-1,N)/fs

freqmod = np.linspace(fl,fu,N)

signal = np.sin( 2*np.pi*(t))

X = signal

# samples between -1 and +1

for i in range(0,len(rgdSamples)):

    rgdSamples[i] =float(X[i])

#open device

dwf.FDwfDeviceOpen(c_int(-1), byref(hdwf))

 

if hdwf.value == hdwfNone.value:

    szerr = create_string_buffer(512)

    dwf.FDwfGetLastErrorMsg(szerr)

    print(str(szerr.value))

    print("failed to open device")

    quit()

 

# enable wavegen channel 1, set the waveform to sine, set the frequency to 1 Hz, the amplitude to 2v and start the wavegen

dwf.FDwfAnalogOutNodeEnableSet(hdwf, c_int(0), AnalogOutNodeCarrier, c_bool(True))

# dwf.FDwfAnalogOutNodeFunctionSet(hdwf, c_int(0), AnalogOutNodeCarrier, funcSine)

dwf.FDwfAnalogOutNodeFunctionSet(hdwf, c_int(0), AnalogOutNodeCarrier, funcCustom) 

dwf.FDwfAnalogOutNodeDataSet(hdwf, c_int(0), AnalogOutNodeCarrier, rgdSamples, c_int(nSamples))

dwf.FDwfAnalogOutNodeFrequencySet(hdwf, c_int(0), AnalogOutNodeCarrier, c_double(hzAcq.value/nSamples))

dwf.FDwfAnalogOutNodeAmplitudeSet(hdwf, c_int(0), AnalogOutNodeCarrier, c_double(1))

 

# enable scope channel 1, set the input range to 5v, set acquisition mode to record, set the sample frequency to 100kHz and set the record length to 2 seconds

dwf.FDwfAnalogInChannelEnableSet(hdwf, c_int(0), c_bool(True))

dwf.FDwfAnalogInChannelRangeSet(hdwf, c_int(0), c_double(5))

dwf.FDwfAnalogInAcquisitionModeSet(hdwf, acqmodeRecord)

dwf.FDwfAnalogInFrequencySet(hdwf,hzAcq)

dwf.FDwfAnalogInRecordLengthSet(hdwf, c_double(nSamples/hzAcq.value)) # -1 infinite record length

 

#wait at least 2 seconds for the offset to stabilize

time.sleep(2)

 

print("Starting oscilloscope")

dwf.FDwfAnalogInConfigure(hdwf, c_int(0), c_int(1))

dwf.FDwfAnalogOutConfigure(hdwf, c_int(0), c_bool(True))

cSamples = 0

 

while cSamples < nSamples:

    dwf.FDwfAnalogInStatus(hdwf, c_int(1), byref(sts))

    if cSamples == 0 and (sts == DwfStateConfig or sts == DwfStatePrefill or sts == DwfStateArmed) :

        # Acquisition not yet started.

        continue

 

    # get the number of samples available, lost & corrupted

    dwf.FDwfAnalogInStatusRecord(hdwf, byref(cAvailable), byref(cLost), byref(cCorrupted))

 

    cSamples += cLost.value

 

    # set the lost & corrupted flags

    if cLost.value :

        fLost = 1

    if cCorrupted.value :

        fCorrupted = 1

 

    # skip reading samples if there aren't any

    if cAvailable.value==0 :

        print ("No Values")

        continue

 

    # cap the available samples if the buffer would overflow from what's really available

    if cSamples+cAvailable.value > nSamples :

        cAvailable = c_int(nSamples-cSamples)

 

    # Read channel 1's available samples into the buffer

    dwf.FDwfAnalogInStatusData(hdwf, c_int(0), byref(rgdSamples, sizeof(c_double)*cSamples), cAvailable) # get channel 1 data

    cSamples += cAvailable.value

 

# reset wavegen to stop it, close the device

dwf.FDwfAnalogOutReset(hdwf, c_int(0))

dwf.FDwfDeviceCloseAll()

 

# generate a graph image from the samples, and store it in a bytes buffer

# plt.plot(np.fromiter(rgdSamples, dtype = np.float))

# bio = BytesIO()

# plt.savefig(bio, format="png")

 

plot(t,X,np.fromiter(rgdSamples, dtype = np.float))

 

 

Edited June 22, 2021 by abadialali

[attila]

Hi @abadialali

It is working with the latest beta version:
https://forum.digilentinc.com/topic/8908-waveforms-beta-download/

 

[abadialali]

Thanks! it is working great now, but I still don't seem to be able to trigger the Analog in with the Analog out. Does the trigger work for record or not? 

 

I am using the following code portion: 

 

 

dwf.FDwfAnalogInTriggerSourceSet(hdwf, trigsrcAnalogOut1)

dwf.FDwfAnalogInTriggerAutoTimeoutSet(hdwf, c_double(10.0))

dwf.FDwfAnalogInTriggerTypeSet(hdwf, trigtypeTransition)

dwf.FDwfAnalogInTriggerLevelSet(hdwf,c_double(0.0))

dwf.FDwfAnalogInTriggerConditionSet(hdwf, trigcondRisingPositive)

 

It seems like the Scope always work before the wavegen and it records few samples that causes some phase shift between my generated values and read ones. 
 

[attila]

Hi @abadialali

1. If the analog-in is triggered on analog-out, the analog-out should be started (FDwfAnalogOutConfigure) only after the analog-in is armed, otherwise this will miss the trigger.
dwf.FDwfAnalogInTriggerSourceSet(hdwf, trigsrcAnalogOut1)
dwf.FDwfAnalogInConfigure(hdwf, c_int(0), c_int(1))
wait(?) or verify analog-in state
dwf.FDwfAnalogOutConfigure(hdwf, c_int(0), c_int(1))

2. If you are generating a periodic signal the analog-in can be triggered by the detector on analog-in channel.
The transition trigger will require setting the conditions, hysteresis, length.
dwf.FDwfAnalogInTriggerSourceSet(hdwf, trigsrcDetectorAnalogIn)
dwf.FDwfAnalogInTriggerTypeSet(hdwf, trigtypeEdge)
dwf.FDwfAnalogInTriggerLevelSet(hdwf,c_double(0.0))

If you are capturing up to device buffer size of samples you can use the normal capture mode, acqmodeSingle.

See the application Help, SDK examples and the manual pdf.

 

 

[abadialali]

Thanks a lot for your quick reply. 

 

What I am interested in doing is letting the Analog In wait for the first generated sample from the Analog Out then start recording, but I am not able to get it to do that even with what you mentioned, I know it works for normal Analog In read but it doesn't seem to work for analog record for some reason and I always lose some values depending on the sampling rate I am operating at. 

 

[attila]

Hi @abadialali

Please take a look at the AnalogOutIn_PlayRecord.py example found in the WaveForms SDK/ samples/ py